High precision and low cross-coupling laser steering

ABSTRACT

Disclosed is an adjustable mirror mount that is capable of adjusting a mirror in two axes with a high degree of precision and low cross-coupling. Long horizontal and vertical adjustment arms are used to allow the precision adjustment about both a horizontal axis and a vertical axis.

INCORPORATION BY REFERENCE

An Application Data Sheet is filed concurrently with this specificationas part of the present application. Each application that the presentapplication claims benefit of or priority to as identified in theconcurrently filed Application Data Sheet is incorporated by referenceherein in its entirety and for all purposes.

BACKGROUND

Optical systems are used in a large number of analytical devices forvarious purposes, such as identifying and/or characterizing particles,such as cells, in flow cytometry systems. Many optical systems, such asflow cytometers, require careful steering of laser beams to operateproperly. If a laser beam in a flow cytometry system is misaligned, evenby a small amount, the system sensitivity may be degraded or thesystem's ability to characterize particles may cease to function. Thepresent disclosure relates to a laser steering device for compactoptical systems.

SUMMARY

One aspect of the disclosure pertains to an adjustable mirror mount forrotating a reflection surface of a mirror. In some embodiments, anadjustable mirror mount may include: (a) a mirror holder configured tohold a mirror such that a reflection surface of the mirror is parallelwith a horizontal axis, (b) a vertical adjustment arm rigidly connectedto the mirror holder, (c) a horizontal adjustment arm coupled to thevertical adjustment arm by one or more vertical pivots, allowing thevertical adjustment arm to rotate about the horizontal axis relative tothe horizontal adjustment arm, (d) a horizontal pivot pin that iscoupled with the horizontal adjustment arm and has a center axis alignedwith a vertical axis passing through the reflection surface, (e) a cleatthat is adjustably coupled to the horizontal adjustment arm, (f) ahorizontal adjustment screw that changes the separation distance betweenthe horizontal adjustment arm and the cleat causing the horizontaladjustment arm and the mirror holder to rotate about the vertical axisrelative to the cleat when the horizontal pivot and the cleat are heldin fixed locations, and (g) a vertical adjustment screw that changes theseparation distance between the vertical adjustment arm and thehorizontal adjustment arm and causes the vertical adjustment arm and themirror holder to rotate about the horizontal axis.

In some embodiments, a spring may connect the cleat with the horizontaladjustment arm and apply a biasing force to the horizontal adjustmentarm. In some additional or alternative such embodiments, a spring mayconnect the vertical adjustment arm with the horizontal adjustment armand apply a biasing force to the vertical adjustment arm.

In some additional embodiments, at least one of the one or more verticalpivots may include a pivot ball or a pivot rod. In some additional oralternative such embodiments, the horizontal pivot may include a rod orpin.

In some embodiments, the tip of the vertical adjustment screw may pressagainst a sapphire pad located on the horizontal adjustment arm or thevertical adjustment arm. In additional or alternative such embodiments,the tip of the horizontal adjustment screw may press against a sapphirepad located on the horizontal adjustment arm or the cleat.

In some embodiments, the horizontal adjustment arm may have a rigidsupport structure having one or more support columns on which the one ormore vertical pivots are located, and in some further such embodimentsthe vertical adjustment arm may pass through this rigid supportstructure.

In some embodiments, the perpendicular distance between the horizontalaxis and the reflection surface may be less than about 15 mm, and insome further such embodiments the distance may be less than about 8 mm.

In some embodiments, the mirror may have a second surface facing awayfrom the reflection surface, and the adjustable mirror mount may have anopening that is configured for light transmission into the secondsurface and out of the reflection surface. In some embodiments, theadjustable mirror mount may be configured such that light beams at anangle less than about 50°, less than about 40°, or less than about 30°relative to the reflection surface may pass through the second surfaceand out of the reflection surface without being occluded by the mirrorholder.

In some embodiments, the adjustable mirror mount may be configured suchthat light beams are reflected off the reflection surface without beingoccluded by the mirror holder when the angle of the incident light beamrelative to the reflection surface is less than about 50°, less thanabout 40°, or less than about 35°.

In some embodiments, the vertical pivot arm length between thehorizontal axis and the vertical adjustment screw may be in the range ofabout 35 mm to about 45 mm. In some other or additional embodiments, thehorizontal pivot arm length between the vertical axis and the horizontaladjustment screw may be in the range of about 50 mm to about 55 mm.

In some embodiments, the vertical pivot on the adjustable mirror mountmay be configured to permit the reflective surface to be rotated atleast 3° about the horizontal axis.

In some embodiments, the vertical adjustment screw and the horizontaladjustment screw may have between about 40 and about 100 threads perinch or metric equivalents within this range.

In some embodiments, the length of the adjustable mirror mount along thehorizontal axis may be between about 1 inch and about 2 inches.

In some embodiments, the adjustable mirror mount may have an overallshape substantially in the shape of a T when viewed along a directionparallel to the vertical axis, the T having a stem portion thatsubstantially bisects a cap portion that is transverse to the stemportion and forming an interior corner between the cap portion and eachside of the stem portion. In such embodiments, The mirror holder may bein the cap portion and the horizontal adjustment arm may be in the stemportion, and the adjustable mirror mount may be configured such that anidentical, separate adjustable mirror mount is positionable with an endof the cap portion for the identical, separate adjustable mirror mountlocated in one of the interior corners of the adjustable mirror mountsuch that a single optical line-of-sight passes through the mirrorholders of both adjustable mirror mounts.

In some embodiments, the adjustable mirror mount may have an overallshape substantially in the shape of an L when viewed along a directionparallel to the vertical axis, the L having a stem portion and a capportion that is transverse to the stem portion. In such embodiments, aninterior corner may be defined between the cap portion and the stemportion, the mirror holder may be in the cap portion and the horizontaladjustment arm may be in the stem portion, and the adjustable mirrormount may be configured such that an identical, separate adjustablemirror mount is positionable with an end of the cap portion for theidentical, separate adjustable mirror mount located in one of theinterior corners of the adjustable mirror mount such that a singleoptical line-of-sight passes through the mirror holders of bothadjustable mirror mounts.

In some embodiments, the cleat and horizontal pivot may be configured tobe attached to an optical breadboard.

Another aspect of the present disclosure pertains to a system foraligning laser beams that may be characterized by: (a) two or morelasers having different wavelengths; (b) at least one adjustable mirrormount configured with a dichromic mirror that is configured to reflect alaser beam and allows at least one laser beam to pass through the mirrorsuch that the reflected and transmitted beams form a combined beam; and(c) a targets location where the combined beam is directed that isconfigure such that all the optical beam pathways are less than 50 cm.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an implementation of an example arrangement ofa plurality of example adjustable mirror mounts as may be found in anexample flow cytometer.

FIG. 2 is a plan view of a plurality of example adjustable mirrormounts.

FIG. 3 is a plan view of another plurality of different exampleadjustable mirror mounts.

FIGS. 4 a and 4 b are illustrations of the manner in whichcross-coupling can occur.

FIG. 5 is a view of an embodiment of an adjustable mirror mount.

FIG. 6 is another view of the embodiment of the adjustable mirror mountof FIG. 5 .

FIG. 7 is another view of the embodiment of the adjustable mirror mountillustrated in FIG. 5 .

FIG. 8 is a sectional view of the embodiment of the adjustable mirrormount of FIG. 5 .

FIG. 9 is a view of a portion of the embodiment of the adjustable mirrormount of FIG. 5 .

FIG. 10 is another view of a portion of the embodiment of the adjustablemirror mount of FIG. 5 .

FIG. 11 is a cutaway view of the embodiment of the adjustable mirrormount of FIG. 5 .

FIG. 12 is a sectional side view of the embodiment of the adjustablemirror mount of FIG. 5 .

FIG. 13 is another sectional view of the embodiment of the adjustablemirror mount of FIG. 5 .

FIG. 14 is a view of another embodiment of an adjustable mirror mount.

FIG. 15 is another view of the embodiment of an adjustable mirror mountof FIG. 14 .

The Figures are drawn to scale within each Figure, although the scalefrom Figure to Figure may vary.

DETAILED DESCRIPTION

In the following description, specific details are set forth in order toprovide a thorough understanding of the presented concepts. Thepresented concepts may be practiced without some or all of thesespecific details. While some concepts will be described in conjunctionwith the specific embodiments, it will be understood that theseembodiments are not intended to be limiting. As used herein “each” or“every” may refer to every member of a multiple-member group or to theonly member of a single member group, e.g., use of “each” in the contextof a group that can have one or more members should not be understood toimply that the group has at least two members. It is to be understoodthat the use of relative terms such as “above,” “on top,” “below,”“underneath,” etc. are to be understood to refer to spatialrelationships of components with respect to the orientations of thosecomponents when the adjustable mirror mounts discussed herein aremounted to a horizontal surface—although such adjustable mirror mountsare also mountable to surfaces in any orientation, and it is to beunderstood, for example, that a component that is “above” anothercomponent when mounted to a horizontal surface does not cease to be“above” the other component when the horizontal surface is turned upsidedown.

Flow cytometry systems analyze the physical and chemical characteristicsof particles in a fluid as the particles in the fluid pass through atleast one laser beam. Beam steering systems are utilized in flowcytometry systems to direct laser beams so that they intersect a fluidsample containing particles at an appropriate measurement location; thisintersection of the fluid sample with the laser beam is also called“interrogation.” To minimize sensitivity degradation resulting fromoptical losses, it is desirable that the beam length from emission pointto sample intersection point of each sample-interrogating laser in aflow cytometry system be minimized. When a plurality of lasers is usedin a flow cytometry system, it becomes important for whatever beamsteering systems are used to have a small footprint so that the opticalpaths do not become too long, which increases beam dispersion andnegatively impacts system operation. It is also important for beamsteering systems to allow for simple user adjustment so that aninstaller can quickly and accurately adjust the laser beam paths. Whilecommercially available beam steering systems may be used in suchapplications, these mounting systems are large and result in long beampaths when used, and/or they introduce axis cross-coupling and may bedifficult to configure. Axis cross-coupling occurs when rotation of amirror about an axis results in a translation of the reflected beam. Forexample, if a mirror is rotated about a horizontal axis it may also betranslated slightly in the horizontal plane. This cross-coupling effectmakes it more difficult for a user to configure lasers in a flowcytometry system, as even minute lateral shifts of a laser beam maycause it to no longer illuminate the desired measurement location in thefluid sample. The adjustable mirror mount disclosed herein is an elegantsolution that reduces cross-coupling while providing compact beamsteering for applications such as flow cytometry systems.

FIG. 1 illustrates an implementation of an example adjustable mirrormount in a flow cytometry system. As shown in FIG. 1 , a plurality oflasers 166, 168, 170, 172, 174 are located in an instrument, such as aflow cytometer, in very tight quarters. The laser beams 176, 178, 180,182, 184 for lasers 166-174, respectively, are to be combined into asingle combined beam 194. In some embodiments, the lasers 176-184 may bevertically separated within the combined beam, e.g., by 50 μm to about100 μm each, when focused. A plurality of adjustable mirror mounts 186,188, 190, 192, and 193 may be used to combine these beams into thecombined beam 194, which is directed at a measurement location 195, witha high degree of precision, i.e., on the micron scale. In a flowcytometry system, the measurement location is typically a cuvettethrough which a sample fluid passes containing the particles beingcharacterized—the sample fluid may be hydrodynamically focused withinthe cuvette to cause the particles of interest to occupy only a verysmall volume within the cuvette. As can be seen, in order to make thebeam steering assembly relatively compact, the adjustable mirror mounts186-192 may be spaced very closely in their lateral directions, e.g.,directions parallel to the reflection surfaces of the mirrors held inthe mirror mounts, so that the adjustable mirror mounts 186-192 overlapin some lateral locations along their lateral directions. However, thelength of the adjustable mirror mounts 186-192 can be made longer, sothat a higher degree of precision can be provided in adjusting thevarious laser beams 176, 178, 180, 182, 184 even in this compactarrangement of adjustable mirror mounts, such as may be found in a veryconfined space.

FIG. 2 provides an enlarged plan view of the four adjustable mirrormounts 186-192 that are compactly arranged to pass light along acombined beam axis 196. As can be seen by the overlaid letters “T”, 197,the mirror mounts have a “T” shaped layout. The “T” shape has a cap 103(which corresponds to the horizontal part of the letter “T”),corresponding to the mirror holder and generally extending along adirection parallel to the mirror surface. The “T” shape also has a stem105 (which corresponds to the vertical part of the letter “T”),corresponding to the length of the mirror mount in the direction of theadjustment arms. The vertex 111 of the “T” shapes is placed at thereflection point of the mirror and the “T” has an interior region 113where an adjacent adjustable mirror mount may be placed. This T-shapeddesign allows the adjustable mirror mounts to be closely packedtogether, e.g., nested into one another, such that an adjustable mirrormount may be placed in the interior region of an adjacent adjustablemirror mount while still providing long adjustment arms to make minorrotational adjustments. In some cases the length of an adjustable mirrormount in the direction corresponding to the stem is less than about 6inches, in some cases less than about 4 inches, and in some cases lessthan about 2 inches. The length of the mirror mount corresponding to thecap is sometimes less than about 15%, in some cases less than about 25%smaller, and in some cases less than about 35% smaller than the lengthof the mirror mount in its longer direction.

In some cases, a mirror mount may have a layout that differs somewhatfrom the “T” shape depicted in FIG. 2 , but still allows mirrors to bepacked closely together. For example, in some cases, the angle betweenthe stem and cap of the “T” may be less than 90°. In some other oradditional instances, the stem of the “T” may be shifted to one side orthe other so that the adjustable mirror mount may more closely take theshape of an “L” or “F” (the Greek capital lambda). FIG. 3 depicts howmirror mounts having an L- or F-shaped layout 199 may be arranged topass light along a combined beam axis 196. The “L” shape also has a stem105, corresponding to the length of the mirror mount in the direction ofthe adjustment arms. In this case, the vertex 111 of the “L” shape isoffset from the reflection point of the mirror and the horizontal pivot.The “L” shape has an interior region 113 where an adjacent adjustablemirror mount may be placed. Like the “T” shape, the “L” shape allows theadjustable mirror mounts to be closely packed together, such that anadjustable mirror mount may be placed in the interior region of anadjacent adjustable mirror mount while still providing long adjustmentarms to make minor rotational adjustments.

It is to be understood that the example adjustable mirror mountsdiscussed with respect to FIGS. 2 and 3 may be thought of as beingsubstantially T-shape or L-shaped—they may have protuberances, recesses,or proportions that may detract from these shapes, but it will beunderstood that such adjustable mirror mounts may still reasonable bedescribed as T-shaped or L-shaped and are thus considered to be“substantially” T-shaped or L-shaped. Moreover, it is to be understoodthat the “stem” portion in such adjustable mirror mounts may be moved,for example, to any point between the center of the cap portion, whereit bisects the cap portion, and the end of the cap portion. For aT-shaped adjustable mirror mount, the stem portion may substantiallybisect the cap portion, e.g., divide the cap portion into equal halvesor even into unequal halves, e.g., 40/60.

For a given light beam that reflects off of a mirror, if the mirror isrotated about a horizontal axis or vertical axis (or both such axes)that does not pass through the reflection point, which is the pointwhere the light beam is reflected by the mirror, the reflected lightbeam will be translated in space along an axis of the incident lightbeam due to axis cross-coupling. Axis cross-coupling generally resultsin a spatial displacement of the beam as a result of the spatialdisplacement of the reflection point of the mirror when the optics areadjusted. As such, the beam cannot be easily steered. Spatialdisplacement, or spatial translation, may be acceptable within certainranges depending upon the application of the mirror mount. In somecases, such as in some flow cytometry applications, axis cross-couplingmay be acceptable if it results in a translation of less than about 30microns, in some cases less than about 20 microns, and in some casesless than about 10 microns, through about 3° of beam steeringadjustment. While systems such as gimbal mounts can be used, in theory,to virtually eliminate axis cross-coupling, such systems are veryexpensive and also quite large (e.g., having square or rectangularmounting footprints on the order of 2″ wide by 2″ long or larger)—theyare also difficult to accurately adjust. In the context of a tightpackaging environment, such as in a flow cytometer, the use of gimballedmirror mounts would be prohibitively expensive and would alsoundesirably increase beam path length, thereby reducing opticalperformance of such systems.

FIGS. 4 a and 4 b provide an illustration of axis cross-coupling inwhich a reflected beam is translated when mirror is rotated about anaxis located a distance r from the reflective surface. FIG. 4 a is aperspective viewed along the horizontal axis of rotation, and FIG. 4 bis a view along the vertical axis. As depicted, a mirror 104 is rotatedfrom a first position, marked by letters A/A, having reflection point106 a to a second position, marked by the letters B/B, having reflectionpoint 106 b. The rotation of the mirror around pivot point 101 resultsin a lateral translation of the reflection point equal to a distance xgiven by Equation 1, where r is the perpendicular distance from thepivot point 101 to the reflective surface, θ is the angle that themirror is rotated about pivot point 101. Perpendicular distance is thedistance between two objects as measured along a direction that isperpendicular to one or both objects. In this case the perpendiculardistance is measured along a direction that is perpendicular to thereflective surface and the axis about which pivot point 101 rotates.

x=r(sec θ−1)  Equation (1)

The lateral translation of the reflection point by a distance x resultsin a lateral translation of the beam, y, that is dependent on theincident angle, φ, of the incident beam 108 from the reflection surface.Taking into account the incident angle and the translation of thetranslation of the reflection point, the translation of the reflectedbeam from an initial position 109 a to a final 109 b can be determinedusing Equation 2.

$\begin{matrix}{y = \frac{r( {{\sec\theta} - 1} )}{\sin(\phi)}} & {{Equation}(2)}\end{matrix}$

As can be seen in Equation 2, the lateral cross-coupling effect may bereduced when r is small (and it vanishes completely when r=0). It isdesirable for y to be reduced as beams may incur further translationbefore reaching their target location if they pass through one or moredichroic mirrors. For example, laser beam 176 (FIG. 1 ) may be furthertranslated as a result of passing through the backside of the dichroicmirrors in adjustable mirror mounts 188-192. For most laser steeringapplications, this additional translation caused by passing throughadditional dichroic mirrors is generally insignificant.

FIG. 5 is a view of an embodiment of an adjustable mirror mount 100. Asillustrated in FIG. 5 , a mirror holder 102 a/b holds a mirror 104 in apredetermined position to reflect a light beam, such as light beam 108.Light beam 108 contacts the mirror 104 at a reflection point 106 and isreflected off of the front surface of the mirror 104 as beam 109. Inorder to steer the reflected light beam 109 in the desired direction,the mirror holder 102 a/b may be rotated. Very fine adjustments arerequired to properly steer the light beam 109 in certain applications.In some embodiments, mirror 104 is a dichroic mirror that is configuredfor a transmitted beam 107 to pass through the back surface of themirror and onto beam path 109 or on another path similar to beam path109. When used in a flow cytometer, light beam 108 may be a laser beamthat may be very accurately directed to form a combined beam, e.g., bycombining a transmitted beam 107 and a reflected beam 108. As usedherein, the term “mirror” can be any type of reflective surface,including dichroic mirrors, dichroic filters, mirrors that have areflective coating deposited on the front surface of a substrate such asglass, a partially transmissive mirror, a polished metal surface, or anyother type of reflective surface.

In order to accurately steer the light beam 108, the mirror holder 102a/b may be accurately and very finely rotated about two axes, e.g., avertical axis passing through the reflective surface at the reflectionpoint 106 and a horizontal axis that is parallel to the surface ofmirror 104 and normal to the vertical axis. Typically, the vertical axisand horizontal axis align with the global vertical and horizontalplanes, respectively; however, this need not be the case. For example, amirror mount may be mounted upside-down or on a titled surface. Asdepicted, the vertical axis skims along the surface of the verticallydisposed mirror 104 through the reflection point 106. The horizontalaxis is parallel to an axis that also passes through the center 106 ofthe mirror and skims along the reflective surface of the mirror 104. Thehorizontal axis is offset from the reflection point 106 of the mirror bya distance, r, and is orthogonal to the vertical axis. In someembodiments, the offset distance, r, between the reflection point 106and the horizontal axis is less than about 15 mm, in some embodimentsthe offset distance is less than about 8 mm. In some embodiments, theoffset distance (see 119 in FIG. 12 ) is about 7 mm. As describedelsewhere herein, if the distance r is reduced the translation of areflected beam due to the rotation of a mirror will also be reduced.Rotation of the mirror in the mirror holder about the vertical axiscauses the light beam 108 to be deflected at different angles in thehorizontal plane. Similarly, rotation of the mirror holder about thehorizontal axis deflects the light beam 108 in the vertical plane.

As further shown in FIG. 5 , the horizontal alignment arm 110 has alength that is sufficient to allow the horizontal adjustment screw 112to adjust the mirror 104 about a vertical axis to steer the light beam108 with the accuracy desired to align the light beam 108. Thehorizontal adjustment screw 112 is a fine pitch screw that moveslaterally only a small amount for each rotation of the horizontaladjustment screw 112. The amount that the horizontal adjustment screw112 moves for each complete turn is referred to as the screw pitch (P).The angle (θ) that the horizontal adjustment arm 110 moves is given byEquation 3.

Sin θ=P/L  Equation (3)

where:

P=Pitch of the screw (amount moved by screw for one rotation of screw)

L=Length of the Adjustment Arm (horizontal pivot arm length 146 of FIG.8 )

θ=Angle moved by Adjustment Arm

Accordingly, Equation 3 may be used to determine how far a screw shouldbe rotated to achieve the desired adjustment angle (θ). Clearly, thelonger the horizontal adjustment arm 110, the better the accuracy thatcan be obtained in steering the light beam 109. Generally, an adjustmentscrew can have any pitch desired, although for fine pitch adjustment,pitches of up to about 40 to up to about 100 threads per inch may bepreferable. Mirror mounts used in beam steering systems that combinenumerous laser beams, such as illustrated in FIG. 1 , may not have asignificant amount of space in the lateral directions of the adjustablemirror mounts because of the close spacing of the laser beams that arecombined into a single combined beam. However, there is certainly morespace in a lengthwise direction, such as the lengthwise direction inwhich the horizontal adjustment arm extends, which allows the adjustablemirror mount 100 to extend in the lengthwise direction and create betteraccuracy in steering the light beam 108. As an example, in oneembodiment, the adjustment screw pitch is equal to 0.10 mm while thelength of the horizontal lever arm is 50 mm. Again, these parametersprovide for a high degree of accuracy in directing the light beam.

FIG. 6 is a diagram of the adjustable mirror mount 100 of FIG. 5illustrated from a different view angle. As illustrated in FIG. 6 , theadjustable mirror mount 100 has a mirror holder 102 a/b that holdsmirror 104. The mirror holder is connected to vertical pivots 124 and126 that rotationally couple the mirror holder with the horizontaladjustment arm 110. As shown, vertical pivots 124 and 126 are located oncolumns 136 extending from support structure 135. Support structure 136has an opening that allows vertical adjustment arm 122 to pass throughit. In some embodiments, vertical pivots may be located on pivot flangesof mirror mount 102 b having pivot balls that allow the mirror mount torotate about a horizontal axis passing through the center of the pivotballs so that the mirror 104 is deflected in a vertical direction. Thedeflection of the mirror holder in a vertical direction is achieved bymoving the vertical adjustment arm 122 using a vertical adjustment screw120. As also illustrated in FIG. 6 , a cleat 114 is secured to abaseplate 128 (FIG. 8 ). The horizontal adjustment arm 110 is movedrelative to the cleat 114. Spring 116 holds the tip of the adjustmentscrew in horizontal adjustment arm 110 against the cleat 114.

FIG. 7 is another view of the adjustable mirror mount 100 viewed from adifferent angle. As illustrated in FIG. 7 , the mirror holder 102 a/b isrigidly connected to the vertical pivots 124 and 126 located on supportcolumns 136. Vertical adjustment arm 122 is coupled to the mirror holderand moves in a vertical direction as a result of adjustment of thevertical adjustment screw 120. A vertical gap between support structure135 and the vertical adjustment arm 122 allows the vertical adjustmentarm to move within an adjustment range without interference by thesupport structure 135. FIG. 7 also illustrates the horizontal adjustmentarm 110 and cleat 114.

FIG. 8 is a cross-sectional view of the embodiment of the adjustablemirror mount 100 illustrated in FIG. 5 . As shown in FIG. 8 , theadjustable mirror mount 100 is mounted on a baseplate 128. Thehorizontal adjustment arm 110 is coupled to the baseplate 128 with ahorizontal pivot pin 118. Horizontal pivot pin need not be a pin, butmay be any single axis rotation joint that rotationally couples thehorizontal adjustment arm with the base plate. The horizontal adjustmentarm 110 rotates around the horizontal pivot pin 118 on the baseplate128. The horizontal pivot pin is aligned with the vertical axis 198passing through the reflection point 106. The distance between thecenter of the opening for the horizontal adjustment screw and the centerof the horizontal pivot pin 118 is the horizontal pivot arm length 146.As indicated above, the horizontal pivot arm length 146 controls theamount that the horizontal adjustment screw 112 (FIG. 5 ) must be movedto create a desired rotation of the mirror 104. In other words, a largehorizontal pivot arm length 146 allows for better adjustment and controlof the pivoting of the mirror 104 and mirror holder about a verticalaxis 198 that passes through the reflection point 106 (FIG. 5 ) of themirror 104. In some cases the horizontal pivot arm length is betweenabout 50 mm and about 55 mm. FIG. 8 also illustrates the manner in whichthe mirror holder 102 b is mechanically coupled (e.g., bolted, welded,brazed, soldered, or glued) to the vertical adjustment arm 122; in thiscase, it is by way of a bolted interface. In some cases, parts 102 a and102 b may be held together by a bolted interface. In some cases, mirror104 may be attached to mirror holder 102 a using a glue or epoxy. Asdisclosed above, the vertical adjustment screw 120 adjusts the positionof the vertical adjustment arm 122.

FIG. 9 is a close view of a portion of the adjustable mirror mount 100of FIG. 5 . As illustrated in FIG. 9 , the tip of adjustment screw 112in horizontal adjustment arm 110 is held against the cleat 114 by spring116. The horizontal adjustment screw 112 contacts the cleat 114 toadjust the horizontal adjustment arm 110. Cleat 114 is secured to abaseplate 128 (FIG. 8 ) by a screw and a dowel pin, the end of which canbe seen protruding out of the bottom of the cleat 114. The verticaladjustment screw 120 adjusts the vertical adjustment arm 122. In someembodiments, a mirror mount includes a spring 130 that provides abiasing force to either push or pull the vertical adjustment arm in adownward vertical direction.

FIG. 10 is another top view of an end of the adjustable mirror mount100. As shown in FIG. 10 , the horizontal adjustment screw 112 abutsagainst the cleat 114. While not shown, in some cases the tip ofhorizontal screw 112 is pressed against a sapphire pad or another smoothsurface on cleat 114. Horizontal adjustment spring 132 is in anelongated state so that it provides a biasing force that holdsadjustment screw 112 against the cleat 114. In this manner, thehorizontal adjustment arm 110 is adjustably coupled to the cleat 114,which is secured to the baseplate 128 (FIG. 8 ). While not depicted, insome embodiments adjustment screw 112 may pass through the horizontaladjustment arm and be threaded into cleat 114 such that the adjustmentscrew limits the separation between the horizontal adjustment arm andthe cleat. In such cases, spring 132 is configured to be in a compressedstate and provides a biasing force that pushes the horizontal adjustment110 arm away from cleat 114.

FIG. 11 is another cross-sectional view of the embodiment of theadjustable mirror mount 100 illustrated in FIG. 5 . As illustrated inFIG. 11 , part of the mirror holder is cut away to show a verticalpivot. In one embodiment vertical pivot includes a pivot ball 140 thatsits in a cone-shaped opening 142 on the support column 136 and in acone-shaped opening 138 in a vertical pivot flange of mirror holder 102b. The vertical adjustment arm 122 is coupled to the mirror holder,which in turn is coupled to the horizontal adjustment arm 110 byvertical pivots. As the vertical adjustment arm 122 moves in a verticaldirection, the vertical pivot flange 124 pivots on the pivot ball 140.As can be seen from FIG. 11 , the front surface of the mirror 104 ishorizontally spaced apart from the pivot ball 140. As such, the mirror104 pivots on a horizontal axis 199 that runs horizontally through thepivot ball 140. Movement of the mirror 104 using the vertical adjustmentarm 122 will cause some lateral displacement (x), as illustrated inFIGS. 4 a and 4 b , which will result in a very small amount ofcross-coupling displacement. As also shown in FIG. 11 , the horizontaladjustment arm 110 is coupled to the support column 136, so thathorizontal movement of the horizontal adjustment arm causes the supportcolumn 136 to rotate the vertical pivots 124 and 126 (see FIG. 6 )around a vertical axis 198 (see FIG. 8 ) that passes through the frontreflective surface of the mirror 104 (or that is coincident with thefront reflective surface of the mirror when the mirror is parallel tothe vertical axis). In other words, horizontal translation of thehorizontal adjustment arm 110 moves the support column 136 horizontally,which is transferred to the vertical pivot flange 124 to rotate themirror holder and mirror 104.

FIG. 12 is a side cross-sectional view of the embodiment of theadjustable mirror mount 100 illustrated in FIG. 5 . As shown in FIG. 12, the support column 136 has a cone-shaped opening 142 in which a pivotball 140 is disposed. A cone-shaped opening 138 in mirror holder 102 acenters the pivot ball 140 in the cone-shaped opening 138. Asillustrated in FIG. 12 , the front reflective surface of mirror 104 isspaced apart from the center of the pivot ball 140 by a distance r(marked by distance 119). Because of the flat angles relative to themirrors at which the light beams may be deflected, as illustrated inFIG. 1 , the pivot ball 140 is placed in the location illustrated inFIG. 12 to avoid blocking of the light beam 108, as well as anythrough-beam 107 coming at an angle from behind for a pass-throughadjuster, e.g., a dichroic mirror adjuster. In some cases, a mirrormount is configured so that light beam 108 and/or through-beam 107 willnot be occluded by the mirror holder 102 a when having incident anglethat is less than about 50° from the mirror surface. In some cases, beam108 or 107 may be directed at mirror 104 at an angle less than about 40°or less than about 35° from the mirror surface without being occluded bythe mirror holder. If the vertical pivots were located on the side ofthe mirror 104, the light beam 108 could be blocked for many packagingarrangements. Consequently, spacing the pivot point at a small distance(e.g., 7 mm) from the front reflective surface of the mirror or filterallows for sufficient precision for guidance of the light beam 108 (FIG.5 ), so that cross-coupling is not a problem, but still allows forinterference-free beam passage.

As also illustrated in FIG. 12 , horizontal adjustment arm 110 isconnected to the support column 136. Rotation of the horizontaladjustment arm 110 transfers the movement to the support column 136,which in turn transfers the rotation to the pivot ball 140 and mirrorholder 102 a/b to rotate the mirror 104 about a vertical axis. Verticaladjustment of the mirror 104 is caused by turning the verticaladjustment screw 120, which moves the vertical adjustment arm 122 in avertical direction. The perpendicular distance between the horizontalaxis passing through vertical pivots (124 and 126) and the axis ofvertical adjustment screw 120 is the vertical pivot arm length 121. Thislength is the length that is effective in causing the mirror 104 torotate around a horizontal axis 199 (see FIG. 11 ) that extends throughthe middle of the pivot ball 140. In some cases the vertical pivot armlength is between about 35 mm and about 45 mm.

FIG. 13 is a cross-sectional view of the embodiment of an adjustablemirror mount 100 illustrated in FIG. 5 . As shown in FIG. 13 , themirror holder holds the mirror 104. The mirror holder is connected tothe vertical adjustment arm 122 by way of bolt 148. Support column 136is protrudes from support structure 135 which is coupled to thehorizontal adjustment arm 110. Vertical adjustment arm 122 is heldagainst the horizontal adjustment arm 110 by way of spring 150, whichalso holds the flanges to the support column, trapping the pivot ballsin the correct location. Vertical adjustment screw 120 adjusts a contactball 152 that engages a ball or rod 154 to adjust the vertical height ofthe vertical adjustment arm 122. In some cases, instead of engaging aball or rod a contact ball engages a planar surface, e.g., a sapphirepad oriented perpendicularly to the adjuster screw axis.

FIG. 14 is a view of another embodiment of an adjustable mirror mount155. As shown in FIG. 14 , the horizontal adjustment arm 156 is pulledtoward a stationary cleat 160 by spring 158.

FIG. 15 provides another view of the adjustable mirror mount 155depicted in FIG. 15 . As shown in FIG. 15 , an adjustment screw 162 ismounted in the cleat 160 to adjust the position of the horizontaladjustment arm 156. Spring end 164 illustrates the manner in which thespring is secured to the cleat 160. In this manner, in tight locations,the embodiment of FIGS. 14 and 15 can be utilized to adjust thehorizontal adjustment arm 110 or 155 from either side of a stationarycleat.

The embodiments disclosed therefore provide an adjustable mirror mountthat is capable of adjusting a reflective mirror (or dichroic filter fora pass-through adjuster) in two axes with a high degree of precision andin a confined area. This allows multiple beams from multiple lasers tobe combined into a single combined beam with a high degree of accuracyand precision. Of course, other applications of the adjustable mirrormount can be used including using the principles disclosed to adjustother optical components, including lenses.

The foregoing description of the invention has been presented forpurposes of illustration and description. It is not intended to beexhaustive or to limit the invention to the precise form disclosed, andother modifications and variations may be possible in light of the aboveteachings. The embodiment was chosen and described in order to bestexplain the principles of the invention and its practical application tothereby enable others skilled in the art to best utilize the inventionin various embodiments and various modifications as are suited to theparticular use contemplated. It is intended that the appended claims beconstrued to include other alternative embodiments of the inventionexcept insofar as limited by the prior art.

1. A flow cytometry system comprising: a measurement location; one ormore adjustable mirror mounts, each mirror mount including acorresponding mirror; and one or more lasers, wherein: each laser of theone or more lasers is oriented so as to emit a corresponding laser beamtowards the mirror of a corresponding one of the one or more adjustablemirror mounts, and the mirror of each adjustable mirror mount of the oneor more adjustable mirror mounts that has one of the one or more laserbeams directed thereat is oriented such that the laser beam directedthereat is reflected off of the reflection surface of that mirror andtowards the measurement location.
 2. The flow cytometry system of claim1, wherein the one or more adjustable mirror mounts includes a pluralityof adjustable mirror mounts.
 3. The flow cytometry system of claim 2,wherein the mirrors of at least some of the adjustable mirror mounts aredichroic mirrors.
 4. The flow cytometry system of claim 3, wherein atleast some of the adjustable mirror mounts with dichroic mirrors arepositioned such that an axis that passes through those dichroic mirrorsintersects with the measurement location.
 5. The flow cytometry systemof claim 3, wherein: the plurality of adjustable mirror mounts includesa first adjustable mirror mount, a second adjustable mirror mount, and athird adjustable mirror mount, the one or more lasers includes a firstlaser and a second laser, the first adjustable mirror mount, the secondadjustable mirror mount, and the first laser are positioned such thatthe corresponding laser beam emitted from the first laser intersects themirrors of the first adjustable mirror mount and the second adjustablemirror mount, an axis passing through the measurement location and themirror of the second adjustable mirror mount does not intersect themirror of the first adjustable mirror mount, the second laser ispositioned such that the corresponding laser beam emitted by the secondlaser intersects the mirror of the first adjustable mirror mount and isreflected so as to strike the mirror of the second adjustable mirrormount, and the mirror of the second adjustable mirror mount reflects thelaser beams emitted by the first laser and the second laser towards themeasurement location.
 6. The flow cytometry system of claim 5, wherein:the plurality of mirror mounts further includes at least a thirdadjustable mirror mount, the one or more lasers further includes a thirdlaser, the third adjustable mirror mount and the second adjustablemirror mount are both arranged such that the mirrors of the thirdadjustable mirror mount and the second adjustable mirror mount intersectwith an axis that passes through the measurement location, the thirdlaser is positioned such that the corresponding laser beam emitted bythe third laser intersects the mirror of the third adjustable mirrormount and is reflected through the mirror of the second adjustablemirror mount and into the measurement location.
 7. The flow cytometrysystem of claim 1, wherein the measurement location is a cuvette.
 8. Theflow cytometry system of claim 1, wherein each adjustable mirror mountincludes: a mirror holder, a cleat, a horizontal adjustment armconnected to the mirror holder, and a mirror having a reflectionsurface, wherein: the mirror holder holds the mirror, and the horizontaladjustment arm and the mirror holder are configured to rotate relativeto the cleat and about a vertical axis that passes through thereflection surface, a stem portion that includes the horizontaladjustment arm, a cap portion that is transverse to the stem portion andthat includes the mirror holder, and an interior corner region formedbetween the cap portion and a first side of the stem portion.
 9. Theflow cytometry system of claim 8, wherein, for at least one adjustablemirror mount of the one or more adjustable mirror mounts, thatadjustable mirror mount: has an overall shape substantially in the shapeof a T when viewed along a direction parallel to the vertical axis ofthat adjustable mirror mount, the stem portion of that adjustable mirrormount substantially bisects the cap portion of that adjustable mirrormount, the T forms an interior corner region between the cap portion ofthat adjustable mirror mount and the first side of the stem portion ofthat adjustable mirror mount, and the T forms a second interior cornerregion formed between the cap portion of that adjustable mirror mountand a second side of the stem portion of that adjustable mirror mount.10. The flow cytometry system of claim 9, wherein at least one of theone or more adjustable mirror mounts that has an overall shape in theshape of a T when viewed along the vertical axis thereof has a stemportion that bisects the cap portion into equal halves.
 11. The flowcytometry system of claim 8, wherein: the at least one of the one ormore adjustable mirror mounts that has an overall shape in the shape ofa T includes a first adjustable mirror mount and a second adjustablemirror mount, and the cap portion of the second adjustable mirror mountlies at least partially within the interior corner region of the firstadjustable mirror mount.
 12. The flow cytometry system of claim 11,wherein: the at least one of the one or more adjustable mirror mountsthat has an overall shape in the shape of a T further includes a thirdadjustable mirror mount, and the cap portion of the third adjustablemirror mount lies at least partially within the interior corner regionof the second adjustable mirror mount.
 13. The flow cytometry system ofclaim 12, wherein a single optical line-of-sight passes through themirror holders of the first, second, and third adjustable mirror mounts.14. The system of claim 8, wherein, for at least one adjustable mirrormount of the one or more adjustable mirror mounts, that adjustablemirror mount: has an overall shape substantially in the shape of an Lwhen viewed along a direction parallel to the vertical axis of thatadjustable mirror mount, and the L forms the interior corner regionbetween the cap portion of that adjustable mirror mount and the firstside of the stem portion of that adjustable mirror mount.
 15. The flowcytometry system of claim 8, wherein: the at least one of the one ormore adjustable mirror mounts that has an overall shape in the shape ofan L includes a first adjustable mirror mount and a second adjustablemirror mount, and the cap portion of the second adjustable mirror mountlies at least partially within the interior corner region of the firstadjustable mirror mount.
 16. The flow cytometry system of claim 15,wherein: the at least one of the one or more adjustable mirror mountsthat has an overall shape in the shape of an L further includes a thirdadjustable mirror mount, and the cap portion of the third adjustablemirror mount lies at least partially within the interior corner regionof the second adjustable mirror mount.
 17. The flow cytometry system ofclaim 16, wherein a single optical line-of-sight passes through themirror holders of the first, second, and third adjustable mirror mounts.18. The flow cytometry system of claim 8, wherein each adjustable mirrormount further includes: a vertical adjustment arm rigidly connected tothe mirror holder, a horizontal pivot coupled with the horizontaladjustment arm and having a center axis aligned with the vertical axis,a horizontal adjustment screw, and a vertical adjustment screw, wherein:the mirror holder is further configured to hold the mirror such that thereflection surface of the mirror is parallel with a horizontal axis, thehorizontal adjustment arm is coupled to the vertical adjustment arm byone or more vertical pivots that allow the vertical adjustment arm torotate about the horizontal axis relative to the horizontal adjustmentarm, rotation of the horizontal adjustment screw changes a separationdistance between the horizontal adjustment arm and the cleat and causesthe horizontal adjustment arm and the mirror holder to rotate about thevertical axis relative to the cleat when the horizontal pivot and thecleat are held in fixed locations, and rotation of the verticaladjustment screw changes a separation distance between the verticaladjustment arm and the horizontal adjustment arm and causes the verticaladjustment arm and the mirror holder to rotate about the horizontalaxis.
 19. The flow cytometry system of claim 1, wherein the mirror of atleast one of the one or more adjustable mirror mounts is anon-transmissive mirror.
 20. The flow cytometry system of claim 1,wherein the mirror of at least one of the one or more adjustable mirrormounts is a transmissive mirror.